1. Using the 25x rule

Andrew Latham, managing editor at SuperMoney, said his favorite method for calculating retirement money is the 25x rule. The calculation is quite simple — all you have to do is multiply the annual income you think you will need in retirement by 25.

"So, if you estimate you will need $80,000 per year when you retire, aim to save $2 million," he said.

He added that he also supports the 33x rule for savers who want to be on the conservative side, since it assumes a 3% withdrawal rate. With the 33x rule and a target income of $80,000 per year, an early retiree would want to save $2.64 million before they leave their job.

https://www.businessinsider.com/personal-finance/tips-experts-calculating-retirement-number-2021-12